An Improved Target Method to Quantitatively Measure the Lateral Resolution of the Confocal Raman Microscope

The lateral resolution is one of the most important hallmarks for evaluating the imaging performance of a confocal Raman microscope (CRM). A method based on the resolution test chart for testing the lateral resolution of the CRM was proposed. The test imaging target comprised a polished silicon substrate coated with a thin metallic pattern, which provided a high contrast and negligible edge effects. By using a single-bar target instead of a conventional three-bar target, quantitative measurements of the lateral resolution of the CRM were possible. Single-bar targets with different widths were used to test a CRM with a nominal lateral resolution of approximately 1 μm. The response of the CRM to the single-bar target was studied further with a theoretical model, and the relationship between the Michelson contrast of the response function and the lateral resolution was investigated. Finally, the method used to calculate the lateral resolution was described and tested and shown to have a relative repeatability of only 5.6%, which is ideal for resolution testing. Overall, our experimental results showed excellent agreement with simulation results and proved that the single-bar target method was capable of measuring the lateral resolution of CRMs with high accuracy, efficiency and reproducibility.